A trip of Asian experts are calling on President Barack Obama to add Seoul, Korea to his upcoming April visit to Asia.

Richard Armitage, former deputy secretary of state, and Victor Cha, former director for Asian affairs on the National Security Council staff, and Michael Green, former senior director for Asian affairs on the NSC, wrote an op-ed published in the Washington Post Friday. All three are affiliated with the Center for Strategic and International Studies.

The White House has not announced Obama's trip, but he is expected to visit Asia following his cancelled trip last fall during the federal government shutdown. He is expected to visit Japan, the Philippines and Malaysia.

The op-ed outlines why visiting South Korea is strategically important for the United States and for U.S. allies in the region as Obama looks to fulfill his administration's pivot to Asia.